Strengthen and expand your shoulder internal rotation end range with PAILs and RAILs in a quadruped position — a precise, well-loaded drill that uses the opposite hand as a passive lever to achieve end-range shoulder IR and then trains the tissue to own and extend that range through targeted isometric loading and immediate range re-testing.

In a quadruped base, the elbow of the working arm is placed either on the floor or elevated on a block. The opposite hand presses the working arm and shoulder into internal rotation, acting as an anchor that passively achieves end range. The shoulder must stay stacked directly on top of the elbow throughout — no leaning, no tilting, no shifting of the torso to assist the rotation. From this honest, stacked position, the passive stretch is held to allow the tissues to accept the load before any contraction begins.

From this passively loaded end-range position, the drill moves through two distinct isometric phases followed by an immediate range re-test: for PAILs, attempt to rotate the shoulder out of IR — pushing against the blocking hand — without any actual movement occurring. For RAILs, actively try to rotate the shoulder deeper into IR — driving further into the range using the internal rotators themselves. After the RAILs contraction, the opposite hand returns and attempts to push the shoulder passively deeper into IR, capturing the newly acquired range that the contractions have created.

PAILs (Progressive Angular Isometric Loading) contract the shoulder external rotators — the muscles being stretched at IR end range — building tensile strength and tissue resilience directly through the lengthened tissue. The blocking hand creates an immovable anchor, ensuring the contraction is purely isometric. RAILs (Regressive Angular Isometric Loading) then fire the internal rotators — the short-side, regressive tissue — actively pulling the shoulder deeper into IR range. The re-test that follows is the critical final step — immediately after the RAILs contraction, the nervous system has been primed and the tissue has been conditioned, making this the optimal moment to push passively deeper and consolidate the newly available range. This three-phase sequence — PAILs, RAILs, re-test — is the complete cycle of end range expansion.

Expect significant effort through the posterior shoulder and external rotators during PAILs as they push hard against the blocking hand. During RAILs, expect a deep, concentrated contraction through the front of the shoulder and internal rotators as the arm actively drives further into IR. The re-test after RAILs should feel like new territory — a deeper passive range that was not available before the contractions. The shoulder must stay stacked on the elbow throughout all three phases — any leaning or compensation immediately compromises the position and the stimulus. Over time, this drill permanently expands shoulder IR range and builds the active strength to back it up — translating to better overhead mechanics, healthier rotator cuff function, and improved performance in throwing, swimming, and pressing.